These are my tips for new players starting Marathon

1. Conserve you ammo in the first missions. Let the enemy come close in easy fights.

2. Don't be afraid to use your grenades or bigger guns for mobs

3. Aim from the middle of your screen not down the sight of the gun

4. Watch the corners. Melee enemies often hide round corners.

5. Check your map. Look for blank areas that you haven't explored.

6. Make note of the save points when you see them. Use it before you leave the level.

7. Make note of the health points when you see them

8. Avoid pincer attacks where you can.

9. Don't be afraid to fall back. This can be a good way to take on the enemy one at a time.

10. Buttons act differently, if it can be activated again after a few seconds it likely means you need to get to a platform or door in time or carry out another action.